Electric meter



(No Model.) 2 Sheet-s-Shee't'l. I E. THOMSON.

ELECTRIC METER.

No, 578,430. Patented Mar. 9,1897;

(No Model.)

2 sheets sheet 2. E. THOMSON. ELECTRIC METER.

Patented Mar. 9, 1897.

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the consumption of energy in a circuit upon fore responds, to thepotential of the mains,

UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE THOMSON- HOUSTONELECTRIC COMPANY, OF CONNECTICUT.

ELECTRIC METER.

SPECIFICATION forming part of Letters Patent No. 578,430, dated March 9,1897.

Application filed August ZG, 1889.

To all whom, it Wmy concern:

Be it known that I, ELIHU THOMSON, of the city of Lynn, county of Essex,and State of Massachusetts, have invented certain new and usefulImprovements in Electric Meters, of which the following is aspecification.

My invention relates to that class of electric apparatus which isadapted to measure which lamps, motors, or other translating de vicesare employed; and my invention therefore applies to the class. ofdevices called electric'meters.

The object of my invention is to provide a means for simply and easilykeeping a record of the product of the current flowing and potential onan electric circuit feeding groups of lamps or other devices fromalternatingcurrent mains, from transformers, or fromdirect-current-supply mains.

Another object of my invention is to secure freedom from too greatdelicacy of parts, simplicity of construction, and practical accuracy inan electric meter.

I employ, in carrying my invention into practice, a coilwhich respondsto the amount of current flowing through the consumption devices, and Iemploy an armature of considerable resistance which is in circuitbetween the terminals of the supply-mains or in a separate circuit ofconstant current, and theresuch movable armature being directly affectedby the magnetic field set up by the current in the said coil, which isin circuit and conveys current to the consumption devices. I also employa magnetic damper or retarder of the speedof motion of the armature,which magnetic damper acts by the development in it of Foucault currentsor induction-currents in a magnetic field. Various modifications anddifferent embodiments of my invention may be made without departing fromthe essence of the invention. These matters will be more particularlyreferred to in describing the accompanying drawings.

Figure 1 shows a general view of the essential parts embodying myinvention. Figs. 2 andS show modifications. Fig. tshows a still furthermodification adapting the meter to a special kind of registry. Figs. 5and 6 are further modifications in the disposition of the Serial No.321,986. (No model.)

parts somewhat similar to Fig. 4. Fig. 7 is a view embodying similarprinciples to those shown in Fig. 2, but of different construction. 5 5Fig. 8 illustrates a modification in the retarder or damping device.

In Fig. l, X is an upright shaft mounted on delicate pivots, upon whichis carried ascrewgearing for moving a registry or counter sys- 6a tem ortrain D. On this shaft is mounted at some other convenient point anarmature A, composed, preferably, when the instrument is to be used onalternating currents or direct currents ad libitum or for alternatingcurrents alone, of a hollow series of coils without iron, or with verylittle iron, in the interior. These coils are preferably wound in aslarge a hollow figure as the dimensions of the instrument will admit.They are also woundin a similar manner to a Siemens armature or otherform of armature which gives a continuously-rotative effect when usedwith a commutator C.

The commutator C is made of as small diameter as practicable, and thebrushes bearing on it are delicate springs carrying small blocks ofmetal, or, preferably, carbon, resting on diametrically opposite pointson the commutator, on a line at right angles, or nearly so, to thecommon axis of the large coils K K, which surround the armature closelyand as closely as possible envelop it. These coils are made of coarseenough wire to carry the full load of current to be measured withoutmuch drop in electromotive force and without heating. The structure asthus constituted is amotor without iron cores, or with very little ironin its structure, so as not to give induction or reactive effects whenalternating currents flow through it. It is connected so that the coilsK K, either in series or multiple arc with each otherin the circuitdirect to the lights or other consumption devices, are traversed by thecurrent feeding the lights or consumption devices or by another currentcorresponding to its amount. They could be traversed bya fractionthereof if adjusted properly.

The armature A is wound with fine wire, there being a considerablenumber of vturns 10o traversed bya very small current in deriva tionaround the lights or other devices, and to limit this current, as wellas to adjust its strength, a resistance R is int'erposed,which is ofgreater or less amount, as needed, or the resistance of the armatureitself might be made sufficient for this purpose.

We thus have constituted a motor of simple construction which isresponsive to the energy supplied to the lights, and its rotative torquewill be in proportion to that energy. The current in the fine wire onthe armature A is so excessively small as not to give trouble at thecommutator O, and the commutator itself may therefore be made soinsignificant in size as not to involve friction, which would interferewith the readings.

In order to give the motor so constituted a work which will beproportional likewise to the speed of rotation, I place upon the shaft Xa device in which Foucault or induced currents may be generated byrevolution, such as a copper disk M, affixed to the shaft X and held atright angles thereto. The edges of the copper disk M run between thepoles of permanent or electric magnets of constant power, which areshaped to embrace or closely envelop the disk M, and of which there maybe one or more according to the damping action required. A small woundarmature on short circuit might replace the disk M. The action is quitesimple. As the load is thrown on or off the speed of rotation of themotor is maintained in almost direct proportion to the load, and thedial registry at D is therefore accelerated or retarded in exact, ornearly exact, proportion with the changes of load. An integrated readingtherefore gives the actual energy supplied in working the lamps orconsumption devices.

The instrument when properly constructed has a range of one to fifty ormore.

In Fig. 2 the same instrument is shown of substantially the sameconstruction, the armature A being wound on a suitable carrier,preferably with little magnetic material in it or with no magneticmaterial, although when continuous currents are alone used the arm ature A may contain considerable magnetic material. In addition to thecoils K K there is in Fig. 3 a parallel Winding of finer Wire S S, whichassists in furnishing the magnetic field in which the armature Arevolves. This winding is supplied with initial energy in shunt aroundthe consumption devices or supplied in any other way or from any sourcewith a small current of initial energy, so as to give an initial field.In fact a winding even traversed by a battery-current would sufficewhere continuous currents alone are to be measured, or a slight-powerpermanent magnet might obviously be employed to replace this initialfield-winding.

WVhere alternating currents are used,it is preferable to supply thisinitial field directly, though it will of course be understood that itmay be supplied indirectly through induction, such as a smallinduction-coil, and, in

fact, the currents delivered to the whole meter may, in the case ofalternating currents, be derived inductively from those which are to bemeasured, the only requirement being that the induced currents berelated proportionally with those which are to be measured. Fig. 2 alsoshows the replacement of the permanent magnets whose poles are presentedto the copper disk M by electromagnets which may be energized in shuntto the mains when continuous currents are to be measured or which may beenergized by a separate battery-current when, as in Fig. 3; alternatingcurrents are to be measured in the other coils of the instrument. Theconnections to the coils which are to be in shunt or derivation to thework may be all in series or they may be in separate derivation from themains, independent from one another, any connection being sufficientwhich supplies the energy to the circuit.

Fig. 2 shows the arrangement with the initial energy or initial fielddevices absent, the dotted lines indicating the application of thepermanent magnet-poles in place thereof. This is only applicable,however, to the measurement of continuous or direct currents.

Fig. 4 shows the structure so modified as to resemble more closely aform of motor in which iron is used. The magnetic poles N S have woundupon them in the ordinary way the coils K K, while the armature A is, asbefore, in circuit through the commutator in derivation to the lights LL through an adjustable resistance R, the armature being wound with afine conductor and either containing no iron or being composed-of aniron armature with laminated plates in the usual way. The retarding-diskM is mounted on the armature-shaft and near the poles N S, and theregistry-gearing is shown symbolized at D. This construction is onlyapplicable to cases in which the registry is desired to be less inproportion with a large load or number of lights L than with a smallnumber, the disk M being run near to the poles N S, which, instead ofbeing constant, as in the previous figures, is subject to variationdirectly in proportion to the amount of current flowing to the lights L.The retarding effect will therefore be an increasing effect, and theregistry will be a decreasing registry per unit of consumption thelarger the load. This is useful in some cases Where it is desired todiscount for heavy loads and make an extra charge for small loads. InFig. 5 the arrangement has about the same-effect, the armature A beingshown as having an inner closed circuited shell M under the .winding andbetween the winding and the core in the interior.

In Fig. 6 the armature A and retarder M are alongside under the samefield-pole, the retarder M being in this case a copper cylinder with orwithout an iron core.

Fig. '7 shows a construction which is in effect similar to that given bythe construction Fig. 2. The armature A revolves between field-polesenergized by the coils K K in series with each other and with the lightsL L.

The magnetic poles cause rotation of the armature A, which is inderivation from the main m through the winding T T on another set ofpoles to the other main 'n, or rather to a connection from such mainthrough the coils K K to the group of lights. This puts the armature Aand the coils TT in series, while they are in shunt to the lightstogether. A revolving mass of metal, such as a copper cylinder or even asolid block of brass, iron, or any other structure in which Foucault orinduced currents may be developed by rotation in a magnetic field, iscarried by the shaft X in front of the poles created by the coils T T.The registry mechanism D is actuated by the rotation of the shaft, asbefore. The windings A T T are, of course, rather fine and calculated tolimit the current which flows to a small amount, while the windings K Kare coarse and will carry the full current readily or a determinedfraction thereof which is required to supply all the lights L L inmultiple. Any increase in the load at L L increases the strength of thepoles N S, while the armature Ais supplied with a constant current, dueto its being in a high-reristance circuit, between the mains m n,assuming, of course, that constant potential is maintained at theterminals or between the mains m n. The torque developed by the armatureunder these conditions will be proportional to the strength of the fieldN S, which is proportional below saturation with the current in thecoils K K. The retardation of the disk M will increase as the speedrises, and proportionally thereto as the field in which it moves issubstantially constant with constant potential between the mains m n.The action, then, will be very similar to that of the arrangement, Fig.1, under changed potentials. In Fig. 1 a change of potential between themains increases the armature-current and thereby increases the tial iscompensated for.

torque and speed of turning. same action of increase of armature-currenttakes place on increase of potential between the mains; but this-effectis counteracted by the increased retardation given by the coils T T,acting on the disk M, which coils T T are also responsive to theincreased potential and increase of field in which the disk M moves, sothat the device, Fig. 1, is an energymeter and responds not only toincrease or decrease of current, but also to increase or decrease of'potential, while the arrangement of Fig. 7 is more strictly acurrent-meter, as the effect of increase or decrease of potenlhe device,Fig. 1, will approximately measure the energy supplied, while that ofFig. 7 will measure simply the current supplied without respondingproportionally to the potential.

It will be understood that other forms and dispositions involving othershapes and arrangements of meter devices and other shapes orarrangements of retarding devices acting on the principle of Foucault,or induced cur- In Fig. 7 the rents or magnetic effects may besubstituted for the elements shown in my present invention, and Itherefore by no means limit myself to the constructions shown, as theycan be widely varied and apparently departed from without affecting theactual principles involved and their relation one to the other. It willalso be understood that in every case in which the retarding disk orconductor M has been shown as revolving it could be replaced by themagnets themselves revolving while the disk M remains stationary, asindicated in Fig. 8, and this structure may be adopted in some cases. Inaddition it will be seen that where the current due to the existence ofconstant potential is of constant strength in the armature portion A ofthe apparatus such current might be supplied from a separateconstant-current source, such as a battery, in the case of directcurrents instead of being taken in derivation from the mains themselves,though I prefer a connection to the mains as more practicable andsimpler.

I am aware that what are called motormeters have been constructed in anumber of different ways and with various arrangements of circuits. I amaware also that they have been provided with retarding devices depending011 fan-wheels moving either in air, gas, or liquid, whereby a definiteloading of the motor is at all times obtained. 1 find, however, thatsuch loading is entirely unsuitable for the purpose, as it does not varyin.

proportion to the torque exhibited by the motor except in such cases inwhich both ar- ,mature and field of the motor vary together.

with the work on the circuit, the rotative effort of which is expendedin giving revolution to a current-generating system, such as a copperdisk (which may be taken as representin g a dynamo-armatu re on closedcircuit) turning in a constant field, whereby the magnetic actionsbecome balanced and the load on the motor varies in direct relation toits torque, so that with a double current passing through thefield-coils of the motor a double speed of rotation is obtained. Foraccuracy of registry, therefore, it is not sufficient that the motor begiven a definite resistance or loading, but it is requisite that theloading shall vary in direct relation with the torque or turning powerof the motoritself, and this I secure in my present invention.

What I claim is- 1. The combination in an electric meter, of a rotatingarmature in a circuit of high resistance in derivation to the work andtraversed by a current which is practically constant for all speeds ofrotation while connected to a source of practically constant potential,a set of coils traversed by, or responding to, the variable current fedto the consumption devices, said coils furnishing a whole or a part ofthe field in which said armature revolves, a retarding device moved bysaid armature consisting of a conductor movable in a magnetic field andconsuming energy of rotation therein, and a registry device for countingthe turns of the revolving armature.

2. In an electric meter,the combination with the arm ature-coilscarrying a practically constant current, of the main field producing orenergizing coils in which a rotating armature moves, and an accessory orinitial field-circuit supplied with current from any suitable sourcesuch as a derived circuit around the consumption devices, a constantbattery-current, or the like.

3. The combination of the following elements in an electric meter, arotating shaft connected with a registry system for recording itsrevolutions, an armature-coil system mounted upon said shaft andprovided with a suitable commutator, connections to said commutator froma circuit in derivation to the consumption devices and having adifference of potential at its terminals substantially constant inamount irrespective of the changes of resistance in the part of thecircuit containing the consumption devices, said armature-circuit beingconstructed as described to be traversed by a very small currentpractically constant in amount although the speed of the motor maychange under variations in the strength of its other element, a fieldfor rotating said armature produced by coils in series with orresponding to the current fed to the consumption devices, and aretarding device carried by said armature-shaft consisting of magnetsand closed conductors in relative movement, whereby Foucault or inducedcurrents or magnetic losses are generated, substantially as described.

4t. The method of measuring electric energy or current which consists inestablishing a field by the current flowing to the devices, causing saidfield to envelop or act upon a rotating-armature-coil system traversedby a current which is substantially constant in amount under allconditions of Working of the meter with variable work, retarding therevolutions of said armature-coil system by a magnetic field acting on aclosed conductor, and counting the revolutions of the rotatingarmaturecoil system, substantially as described.

5. The combination with an electric circuit containing translatingdevices, of an electric motor whose field-energizing coils are in themain circuit to the translating devices, and whose armature is traversedby current maintained substantially constant irrespective of variationsin the work. and consequent change of speed of the motor, said motorhaving a loading or retardation which is substantially m'l under verylow rotations and which increases directly as the speed of rotationincreases.

6. An electric meter for constant-potential circuits having a motorwhose rotative energy depends upon the action of a field variable withthe consumption of current, or number of translating devices in use,said motor having a constant armature, irrespective of the variations inthe working, in combination with a retarding device consisting of anelectric generator of induced currents of variable amount in proportionto the speed of rotation and with a constantor nearly constant field.

7. A meter for alternating electric currents,

consisting of a motor having field-magnet coils connected in series withthe work-circuit, armature coils connected across the work-circuit andcarrying a current which is substantially constant in amount under allconditions ofv working, a counting, registering or indicating deviceoperated by the movements of the armature, and a retarding deviceapplied to the armature.

Signed at Lynn, in the county of Essex and State of Massachusetts, this22d day of August, A. D. 1889.

ELI [-IU THOMSON.

Witnesses:

JOHN W. GIBBONEY, JOSEPH H, JENKINS.

